Abstract

MESO- AND SUBMESOSCALE VARIABILITY WITHIN THE UPWELLING REGIME OFF PERU OBSERVED BY A FLEET OF GLIDERS.

In meso- and submesoscale regimes a strong physical-biogeochemical coupling is thought to exist. A swarm experiment with seven gliders equipped with sensors measuring pressure, temperature, salinity, oxygen and chlorophyll fluorescence was conducted in early 2013 within the upwelling region off Peru. The goal was to study near-coastal pathways for the supply of oxygen from the mixed layer to the oxygen minimum zone. Each glider carried out about one dive per hour measuring two multi-parameter profiles with a lateral resolution of about 500 m. More than 15.000 profiles were recorded during the two-months deployment within a small spatial area to capture both the temporal and spatial variability of the physical and biochemical parameters.
The glider-based data show small-scale structures of different tracers such as salinity and oxygen at different depths. There are pronounced density compensated salinity anomalies at about 150 m depth, where lateral eddy-stirring of the lateral background salinity gradient is suggested as the main formation mechanism. Near the surface, non-density compensated salinity and oxygen intrusions are observed, which reached well below the mixed layer. These structures are found in areas of strong lateral density fronts. This suggests that submesoscale frontal processes are responsible for the observed structures. The role of these meso- and submesoscale processes for the near coastal vertical oxygen supply is discussed.